Process monitoring methods in a plasma processing apparatus, monitoring units, and a sample processing method using the monitoring units

ABSTRACT

A method and apparatus for measuring a potential difference for plasma processing with a plasma processing apparatus that processes a sample by introducing a gas into a vacuum chamber and generates plasma. A light-emitting portion is formed on a measurement-use sample of the sample to be processed and a current flows into the light-emitting portion according to a potential difference that has been generated across the light-emitting portion. An intensity of light emitted from the light-emitting portion according to a predetermined light intensity is measured and a potential difference on the measurement-use sample according to a predetermined light intensity is measured.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. application Ser. No. 09/788,629, filedFeb. 16, 2001, now U.S. Pat. No. 6,759,253, the subject matter of whichis incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates to methods of measuring potentialdifferences and currents, and, more particularly, the invention relatesto methods of measuring the potential difference or the plasma currentdeveloped on the surface of a semiconductor wafer sample, when it isunder plasma processing, during semiconductor manufacturing processes,with the semiconductor wafer located inside a plasma reactor in order tosurface-treat the wafer. Also, the present invention relates to anapparatus for monitoring processes in a plasma processing apparatus byuse of the measured potential difference or plasma current, and to asample processing method that uses the process monitoring apparatus.

In general, during the manufacture of semiconductors, semiconductorwafers need to be subjected to various surface treatment processes, suchas etching, and a plasma reactor that applies electromagnetic waves togenerate a plasma is most commonly used as the surface processingapparatus. For such a plasma reactor, the electromagnetic waves and theplasma generate a strong electric field not only in the space of theplasma reactor, but also on the surface of the semiconductor wafermounted on a processing table (sample mount) within the processingapparatus. When a strong electric field is generated on the surface ofthe semiconductor wafer, the field strength will cause a potentialdifference on the surface of the semiconductor wafer, and if thepotential difference exceeds a predetermined value, the semiconductorwafer may be damaged. It is therefore important to measure the potentialdifference on the semiconductor wafer surface when processing thatsurface using a plasma reactor.

In this case, probing (hereinafter referred to as the first knownmethod) is available as one of the typical methods of measuring theelectric field strength and potential differences occurring inside theplasma reactor. The first known method is intended to measure theelectric field strength and potential differences inside the plasmareactor by inserting conductor probes into a plasma atmosphere and,then, after scanning with the probes, detecting the voltage-currentcharacteristics thereof.

A method of measuring the potential of a semiconductor wafer inside aplasma reactor (hereinafter referred to as the second known method) isdescribed on page 775 of a Japanese-Version Preliminary ArticleCollection at the 46th Association Symposium on Applied Physics, held inthe spring of 1996. For the second known method, the potentialdifference on the semiconductor wafer surface is measured by searchingwith probes embedded directly in the semiconductor wafer (which ismounted on the sample mount, namely, the semiconductor wafer mountingtable, inside the plasma reactor) at a portion where the potentialdifference is estimated to occur, instead of searching with probesembedded in the sample mount itself.

Since the first known method, which proposes to measure the potentialdifference on the semiconductor wafer inside the plasma reactor, is usedto detect the voltage-current characteristics of the conductor probes byscanning in a plasma atmosphere, it is necessary to transmit detectionoutput signals from the conductor probes to an external apparatus byusing connection lead wires and to provide the vacuum chambers withconnection lead wire relay terminals, because the plasma is generatedinside the vacuum chamber. In addition, the total structure of theplasma reactor is complex, and this makes it impossible for thepotential difference on the semiconductor wafer to be measured using asimplified means.

Furthermore, since the second known method, which proposes to measurethe potential difference on the semiconductor wafer inside the plasmareactor, uses probes embedded in a sample mount on which thesemiconductor wafer is to be mounted, it is not only necessary for thesample mount to be of special structure, but it is also difficult toprocess the surface of the semiconductor wafer on this sample mountafter measuring the potential difference on the semiconductor wafer byuse of the sample plate. In addition, the type of sample mount to beused will differ between measurement of potential difference on thesemiconductor wafer and the surface-treatment processing thereof, andthis results in increased plasma reactor costs and, hence, an increasednumber of treatment processes.

SUMMARY OF THE INVENTION

The present invention is directed to such a technical background, andone of its objects is to provide a potential difference and currentmeasuring method that enables the DC potential difference on a targetobject to be measured using a simplified means via a potentialdifference and current measuring arrangement having a simplifiedconfiguration.

Another object of the present invention is to provide a method thatenables samples to be efficiently processed while the processes arebeing monitored using an apparatus having a simplified configuration.

When a light-emitting diode or the like is left in a plasma-exposedatmosphere, the potential difference arising from the resulting flow ofcharged particles (ions and electrons) from the plasma will create theflow of an electric current into the light-emitting diode and activateit to emit light. The light emission intensity of the light-emittingdiode has a constant correlation with the voltage and current of thediode. The present invention utilizes this property.

The present invention is characterized in that, in a method of measuringthe potential differences for plasma processing with a plasma processingapparatus that processes a sample by introducing a gas into vacuumchambers and generating a plasma: a light-emitting portion is formed ona measurement sample; the potential difference generated according tothe difference in the amount of plasma-incident charged particles isdetected; a current flows into said light-emitting portion according tothe potential difference that has been generated across saidlight-emitting portion; the intensity of the light emitted from saidlight-emitting portion according to the particular level of said currentis measured; and the potential difference on said measurement sampleaccording to the particular light intensity is measured.

The present invention is also characterized in that, in a method ofmeasuring the plasma processing potential difference on the object to beplasma-processed by introducing a gas into vacuum chambers andgenerating a plasma: a light-emitting portion is formed on said objectto be plasma-processed; the flow of charged particles from the plasma tothe surface of said object is measured as the intensity of the lightemitted from said light-emitting portion according to the level of thecurrent flowing thereinto; and the amount of current flowing into saidobject according to the particular light intensity is measured.

For example, antennas for acquiring charged particles from plasma to theterminals of the light-emitting portion are connected first. Theseantennas are then installed inside the plasma processing apparatus or onthe wafer, and the light emission intensity of the light-emittingportion is measured. It is possible to measure the potential differencebetween any two positions by establishing the correlation expressionbetween the pre-calculated light emission intensity and voltage-currentcharacteristics of the light-emitting portion and converting the lightemission intensity into a voltage, or to measure the plasma currentbetween any two positions by converting the light emission intensityinto a current using the above-mentioned expression.

To measure the plasma potential difference, the circuit resistance valueof a light-emitting diode needs to be greater than an external circuitresistance including the plasma, or, to measure the plasma current, thecircuit resistance value of the light-emitting diode needs to be smallerthan the above-mentioned external circuit resistance value. This methodrequires only a window for measuring light intensity, and does notrequire lead wires or lead wire lead-in terminals.

In order to fulfill the foregoing objects, a potential differencemeasuring method based on the present invention uses a potentialdifference and current measuring arrangement equipped with one pair ofconductor antennas, a light-emitting portion connected between theconductor antennas, and an AC voltage bypass element connected inparallel to the light-emitting portion, and a means is provided forarranging/connecting the conductor antennas at/to the potentialmeasuring positions on the object to be measured and for measuring theDC potential differences at these potential measuring positions bydetecting the intensity of the resulting light output from thelight-emitting portion.

According to the means described above, after the arrangement andconnection of the conductor antennas at/to the potential measuringpositions on the object to be measured, when DC potential differencesexist at these potential measuring positions, the light-emitting portionor the light-emitting diodes will emit light. The DC potentialdifferences at the potential measuring positions can therefore bemeasured by visually detecting the emitted light intensity from the unitcontaining the target object (for example, from the exterior of theplasma generating layer) through an optical unit, such as acharge-coupled device (CCD) camera. Thus, it is unnecessary to provideconnection lead wires to acquire detection output signals, or a samplemount in which conductor probes for detection are embedded.

In this case, since an AC voltage bypass element (preferably, acapacitor) is connected in parallel to the light-emitting portion, anyAC potential differences between potential measuring positions arebypassed by the AC voltage bypass element and only the DC potentialdifferences at the potential measuring positions can be measured.

The present invention also makes it possible to supply a highlyefficient sample-processing method that uses a potential difference andcurrent measuring portion having a simplified configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an ECR etching apparatus.

FIG. 2 is a top view of the potential difference and current measuringunit representing an embodiment of the present invention.

FIG. 3 is a cross-sectional view of the potential difference and currentmeasuring unit of the present invention.

FIG. 4A is a diagram of the potential difference and current measuringunit illustrating the principles of the present invention.

FIG. 4B is a graph showing the variation in potential different withtime.

FIG. 5 is a graph showing the relationship between the voltage appliedto light-emitting diodes and the intensity of the light emitted from thediodes.

FIG. 6 is a graph of light intensity versus time showing an example ofapplication results produced by the present invention.

FIG. 7 is a graph of potential difference versus high frequency powershowing an example of application results produced by the presentinvention.

FIGS. 8A and 8B are block diagrams of embodiments of the potentialdifference and current measuring unit of the present invention.

FIG. 9 is a top view of semiconductor processing equipment which usesthe potential difference and current measuring unit of the presentinvention.

FIG. 10 is a flowchart of a process intended to improve productivity byapplying the potential difference and current measuring unit of thepresent invention to semiconductor processing.

FIG. 11 is a flowchart of a process intended to apply the potentialdifference and current measuring unit of the present invention to theoptimization of semiconductor processing equipment.

FIG. 12 is a schematic diagram of a potential difference measuring unit,based on the present invention, which does not have a capacitor.

FIG. 13 is a diagram of an ashing apparatus.

FIG. 14 is a schematic diagram of a potential difference measuring unitbased on the present invention.

FIG. 15A is a schematic diagram of a potential difference measuring unitbased on the present invention.

FIG. 15B is a sectional view taken along line A—A in FIG. 15A.

FIG. 16A is a diagram of a potential difference measuring unit based onthe present invention.

FIG. 16B is a cross-sectional view of the potential difference measuringunit of FIG. 16A.

FIG. 17 is a diagram of a potential difference measuring unit based onthe present invention.

FIG. 18A is a schematic diagram of a potential difference measuring unitbased on the present invention.

FIG. 18B is a partial sectional view of the potential differencemeasuring unit of FIG. 18A.

FIG. 19 is a schematic diagram of a potential difference measuring unitbased on the present invention.

FIG. 20 is a schematic diagram of a potential difference measuring unitbased on the present invention.

FIG. 21 is a schematic diagram of a potential difference measuring unitbased on the present invention.

FIG. 22 is a schematic diagram of a potential difference measuring unitbased on the present invention.

FIG. 23 is a diagram of an etching apparatus showing a method ofobserving light emission status in a potential difference measuring unitbased on the present invention.

FIG. 24 is a diagram of an etching apparatus showing the installationlocation for a potential difference measuring unit based on the presentinvention.

FIG. 25A is a top view of a potential difference measuring unit based onthe present invention.

FIG. 25B is a cross-sectional view taken along line A-A′ in FIG. 25A.

FIG. 25C is a cross-sectional view taken along line B-B′ in FIG. 25A.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention will be described with reference tothe drawings.

A diagram of an ECR type of etching apparatus, to which the presentinvention is applied, is shown in FIG. 1. Microwaves are introduced frommicrowave power supply 101 into vacuum chamber 104 via waveguide 102 andwindow 103. The window 103 is made of a material that transmitselectromagnetic waves, such as quartz. Around vacuum chamber 104 thereare arranged electromagnets 107, and the strength of the magnetic fieldsgenerated thereby is set so as to generate a resonance with thefrequency of the microwaves. For example, if the frequency is 2.45 GHz,the magnetic field strength is 875 Gauss. Wafer 105 (or plasma potentialdifference and current measuring unit 200) is mounted on sample mount108. A high-frequency power supply 109 is connected to sample mount 108in order to accelerate the flow of ions into the wafer. The earth ring114 against the high-frequency waves is provided around sample mount108.

Also, in order to measure the light emission intensity of thelight-emitting diodes to be mentioned later, the waveguide has a window112, through which an image of the wafer is monitored using a CCD(charge-coupled device) camera 110. Data that has been acquired by thecamera is processed by personal computer 111. In order to receive thelight emitted from the plasma 106, camera 110 has an interference filter113 adjusted to the light emission wavelength of the light-emittingdiodes.

FIG. 2 is a top view of plasma potential difference and currentmeasuring unit 200 (an embodiment of the present invention), and thismeasuring unit has a potential difference and current measuring devicemounted on a measurement sample of similar material and shape as thoseof the wafer 105 which is to undergo processing. The measuring unit 200is mounted on the sample mount 108. FIG. 3 is a cross-sectional view ofthe plasma potential difference and current measuring unit 200.

Plasma potential difference and current measuring unit 200 has an oxidefilm 205 deposited on a silicon substrate 204, and a light-emittingdiode (LED) 201 is mounted on the oxide film. Aluminum antennas 203 areconnected at both ends of the LED via insulated conductors. The plasmareactor used for etching ranges from 0.5 to 5.0 mA/cm² in saturated ioncurrent density. Since the turn-on current (on-emission energizingcurrent) of the LED 201 is only about 1 mA, the surface areas of theconductor antennas can be set to exceed the range from 0.2 to 2.0 cm².The antenna areas can usually be adjusted according to the particularplasma density.

In this measuring unit, as shown in FIG. 2, there are five groupsincluding one to five light-emitting diodes (LED1 to LED5),respectively, connected in series, and independent antennas areconnected at both ends of each LED group. In this way, the startingthreshold voltage of light emission from each LED group is varied toimprove the measurement accuracy. Each LED group has aparallel-connected capacitor 202 operating as a filter for removing ACvoltage components. The appropriate value of the capacitor is about onemicrofarad when the frequency of high-frequency power supply 109 is 800kHz. Usually, however, it suffices just to change the value according tothe particular frequency. Also, since this example assumes that thepotential in the center of the wafer is greater than that developedaround the periphery of the wafer, the connection polarity is set sothat each diode emits light when potentials are distributed that way.Only in the group where one LED is present, is a reverse polarized diodealso connected in parallel. Thus, detection is possible when thepotential around the wafer is higher.

FIG. 4A shows the distribution of the potentials developed on wafer 105(or plasma potential difference and current measuring unit 200) in theetching apparatus shown in FIG. 1. The nonuniformity of potentials onthe wafer is caused by the nonuniformity of the plasma density and/orthe nonuniformity in the distribution of currents from high-frequencypower supply 109. In FIG. 4A, the potential at the center point A of thewafer is higher than the potential at the edge point B of that wafer byΔVdc. Also, the high-frequency voltage components of high-frequencypower supply 109 overlap on the wafer; and, as shown in FIG. 4B, thepotential between points A and B changes with time. Even if ΔVdc iszero, since each LED emits light with the above-mentioned high-frequencycomponents, capacitor 202 is connected in parallel to LED 201 to ensurethat only the DC component of ΔVdc is measured. Therefore, when themeasuring unit shown in FIG. 2 is installed under plasma processingconditions, the LED will emit light according to ΔVdc.

The relationship between the voltage applied to a series-connected LEDand its light emission intensity is represented in FIG. 5, wherein LED1to LED5 are the identification numbers of the series-connected diodegroups. These diodes emit red light, and the light-emission startingthreshold voltage of one such diode is 1.5 V. When one to five diodesare connected in series in the respective groups, therefore, therespective light-emission threshold voltages are 1.5 V, 3.0 V, 4.5 V,6.0 V, and 7.5 V.

FIG. 6 shows the LED light-emission intensity data measurements usingcamera 110 that were obtained in the case where the plasma potentialdifference and current measuring unit 200 shown in FIG. 2 was installedin the etching apparatus of FIG. 1. The horizontal axis denotes time,and the output of high-frequency power supply 109 was changed in stepsfrom 10 W to 70 W with time. Light-emission intensity data that wasobtained using three connected LEDs, and same data that was obtainedusing five connected LEDs are shown as examples in FIG. 6. It can beseen from this figure that when the three connected LEDs startedemitting light at 20 W, ΔVdc exceeded 4.5 V, and when the five connectedLEDs started emitting light at 50 W, ΔVdc exceeded 7.5 V.

The measurement results on the relationship between high-frequency powerand ΔVdc that were obtained using the above-mentioned method are shownin FIG. 7. The gas was a combination of 74-sccm chlorine and 6-sccmoxygen, and the gas pressure was 0.4 Pa. Also, the output of microwavepower supply 101 was 400 W. These are etching parameters relating to thepoly-silicon used for a semiconductor device.

Since the potential difference (ΔVdc) occurring on the wafer placed inplasma is a quantity related to the insulation breakdown of the gateoxide film on the transistor processed on that wafer, it is important tomeasure ΔVdc. When an etching apparatus is developed or etchingparameters are determined, it is necessary not only that an etching rateand other parameters relating to characteristics be appropriate, butalso that the gate oxide film be free from insulation breakdown.

In the case of prior art, it is necessary that, during the measurementof a potential difference using the probe-embedded electrodes describedin the examples of known methods, an apparatus be designed or etchingparameters be determined so as to minimize the potential difference, andthen the electrodes can be replaced with the normal sample mount to etchthe sample.

In accordance with the present invention, since the unit for measuringΔVdc, namely, the plasma potential difference and current measuring unit200 has the same shape as that of a wafer, it is possible to measureΔVdc without performing any modifications on the etching apparatus, andto etch semiconductor devices just by changing wafers after determiningthe parameters for a sufficiently small value of ΔVdc. In other words,it is possible to reduce the processing time and to analyze etchingcharacteristics, and measure the potential difference inside the wafer,with exactly the same apparatus configuration.

In the embodiment described above, although the antennas at both ends ofeach LED group are arranged in the center of and around the wafer, theseantennas can be moved according to the desired potential differencemeasurement position on the wafer.

Also, the light emission intensity detected by the camera depends onfactors such as the camera-to-LED distance and the light transmittanceof the window material. The absolute potential difference value cantherefore be obtained by measuring the above-mentioned distance andtransmittance and calibrating the detection portion of the camera. Evenif the calibration is not performed, the relative magnitude of thepotential difference inside the wafer can be judged from the lightemission intensity.

Since a distribution curve of the potentials developed on the wafer doesnot always have a humped middle, as shown in FIG. 4A, the polarity ofthe potentials can be judged by mounting one set of forward- andreverse-polarized LEDs in connected form on the wafer.

In FIG. 2, LEDs 201 and capacitors 202 can be shielded with polyimide orthe like, as required, and thus the LEDs and the capacitors can beprotected from plasma-induced damage.

The potentials on the wafer can also be measured together with their ACcomponents by removing capacitors 202. The number of LEDs to beconnected in series in each group can be adjusted (or blue diodes andother diodes different in light emission threshold voltage can be used)according to the particular magnitude of ΔVdc.

Camera 110 for measuring the light emission intensity can be installedinside the vacuum chamber 104 provided with the appropriateelectromagnetic interference countermeasures, and the light-receivingportion can be equipped with an optical fiber. In FIG. 8A,light-emitting circuit 801 is inserted between antennas 203A and 203B,and capacitor 202 is connected in parallel to light-emitting circuit 801to remove AC components. When a potential difference occurs betweenantennas 203A and 203B, since the light-emitting circuit emits lightaccording to the particular potential difference, this value can beidentified by closely observing the quantity of light which has beenemitted. To remove AC components, coil 802 can be connected in series tolight-emitting circuit 801, as seen in FIG. 8B, instead of connectingcapacitor 202 in parallel to light-emitting circuit 801. Thelight-emitting circuit here refers to a circuit that includeslight-emitting diodes 201 or so-called miniature lamps whose resistancevalues change according to the voltage applied across the circuit, orrefers to a laser, such as a semiconductor laser, that includeslight-emitting elements. Various embodiments of this light-emittingcircuit will be described later. Although light-emitting circuit 801that includes light-emitting elements is described here, a unit forgenerating sound waves or electromagnetic waves (such as ultravioletrays, infrared rays, or X-rays) that change in intensity according tothe voltage applied across the circuit can be used, instead oflight-emitting elements. When such a unit is used, however, it is, ofcourse, necessary to use a sensor or filter as well, instead of camera110 or interference filter 113, that can detect those sound wave signalsor electromagnetic wave signals. It is important to provide a means forgenerating some type of physical quantity according to either thevoltage applied across the circuit, or the current corresponding to thevoltage, and a means for detecting the physical quantity at a positionfar from the means mentioned above.

Next, a method of using plasma potential difference and currentmeasuring unit 200 to manufacture semiconductors will be described. Anexample of semiconductor manufacturing equipment is shown in FIG. 9.This equipment includes, more specifically, an etching apparatus, a CVDapparatus, etc.

The semiconductor manufacturing equipment shown in FIG. 9 has processingchamber 901, a second processing chamber 902, a wafer transport robot903, a loading lock chamber 904, an unloading lock chamber 905, a loader906, and a stocker 907. Stocker 907 contains cassettes 908 and a dummycassette 909. When a wafer is processed in processing chamber 901, thewafer 105 within cassette 908 under almost atmospheric conditions istransported to the loading lock chamber 904, which is also under almostatmospheric conditions, by loader 906, and then the loading lock chamberis closed. After the loading lock chamber 904 has been decompressed to asuitable pressure, wafer transport robot 903 transports wafer 105 toprocessing chamber 901, where the wafer is then provided withappropriate processing. After being processed, wafer 105 is transportedto the unloading lock chamber 905 by the wafer transport robot 903.After the internal pressure of the unloading lock chamber 905 has beenincreased nearly to atmospheric pressure, wafer 105 is returned tocassette 908 by loader 906. Such processes are usually repeated.

Next, a method of using plasma potential difference and currentmeasuring unit 200 to process wafers will be described with reference toFIG. 10. Wafers 105 usually undergo processing in processing chambers901 and 902 (S1000). When processing parameters are checked periodicallyor non-periodically, the plasma potential difference and currentmeasuring unit 200, that has been placed in dummy cassette 909beforehand, is transported to the processing chambers, where theprocessing parameters can then be checked (S1002). That is to say, whenthe processing parameters are to be checked, the plasma potentialdifference and current measuring unit 200 that has been placed in dummycassette 909 beforehand is transported to the loading lock chamber 904by loader 906, and then it is transported to the processing chamber 901by wafer transport robot 903. After this, the plasma potentialdifference and current measuring unit 200 is subjected to processingconditions with predetermined parameters and the light emission statusat this time is monitored to confirm the presence/absence of anabnormality and to detect its level (S1004).

When no abnormality is detected, the potential difference and currentmeasuring unit 200 is removed using wafer transport robot 903, and isthen placed in unloading lock chamber 905, from which it is returned tothe dummy cassette 909 by loader 906 to restart semiconductor processing(S1000).

If an abnormality is detected, the processing chambers are maintained ina vacuum state as long as possible and the processing apparatus ischecked and provided with countermeasures (S1006). After thecountermeasures have been undertaken, the plasma potential differenceand current measuring unit 200 is subjected to processing conditionswith predetermined parameters once again and the light emission statusis monitored (S1008) to confirm the presence/absence of an abnormalityand detect its level (S1010).

At this time, when no abnormality is detected, the potential differenceand current measuring unit 200 is removed using wafer transport robot903, and it is then placed in the unloading lock chamber 905, from whichit is returned to the dummy cassette 909 by loader 906 to restartsemiconductor processing (S1000). If an abnormality is detected again atthis time, the potential difference and current measuring unit 200 isremoved using wafer transport robot 903, and it is then placed in theunloading lock chamber 905, from which it is returned to the dummycassette 909 by loader 906. After this, the processing chambers areexposed to the atmosphere and necessary maintenance takes place (S1012).The necessary maintenance here refers more specifically to replacementof consumable parts and removal of sticking film from the varioussections of the processing chambers by use of substances such as anorganic solvent.

After proper maintenance has been performed, the processing chambers areplaced in a vacuum state once again to enable semiconductor processing.At this time, semiconductor processing is not started immediately.Instead, it is started only after it has been confirmed that processingchamber 901 has returned to normal is using the potential difference andcurrent measuring unit 200 (S1014 to S1016). If an abnormality isdetected during this process, it is determined that the processingchamber 901 or the entire semiconductor manufacturing equipment requiresrechecking and that the maintenance processes described above are to beperformed again, and/or more extensive maintenance processes are to beperformed.

Processing parameters relating to the potential difference and currentmeasuring unit 200 of the present invention do not always need to matchthe semiconductor processing parameters. Given the same parameters,whether the parameters are being properly maintained is to be judged.However, the use of the parameters enables easy detection of anabnormality, although these parameters differ from actual processingparameters, and makes it possible to estimate beforehand any abnormalstates that slightly change with the progress of time. Since theseparameters differ from actual processing parameters, semiconductorprocessing does not always need to be stopped, even if an abnormality isdetected. If an abnormality is detected under conditions using theseparameters, however, after semiconductor processing has been restarted,the equipment status monitoring time is to be made shorter than usual,by using the potential difference and current measuring unit of thepresent invention once again. This maintains the equipment availabilityand prevents processed wafers from being wasted.

In the above-described embodiment, although atmospheric cassettes areused for descriptive reasons, vacuum cassettes can also be used instead.

Next, a method of using the potential difference and current measuringunit 200 to develop processing unit 901 or etching processes will bedescribed with reference to FIG. 11. In this case, the potentialdifference and current measuring unit is to be inserted into thesemiconductor manufacturing equipment to be developed, for example, theetching apparatus shown in FIG. 1.

For example, to optimize the height of the sample mount 108 for reducedpotential difference inside the wafer, it is necessary first to keepconstant the output power of the microwave power supply for generatingplasma, the output power of the high-frequency power supply for applyinga bias voltage to the wafer, the internal pressures of the processingchambers, the flow rate of the gas to be introduced into the processingchambers, and other parameters, and then to mount potential differenceand current measuring unit 200 on the sample mount 108 and observe lightemission status. Next, only the height of the sample mount is to bechanged, and the light emission status is to be observed again (S1100).

Parameters that generate an insignificant potential difference insidethe wafer can be found by repeating the above experiments and examiningthe relationship between the height of the sample mount and lightemission status.

This method can be used merely by inserting the potential difference andcurrent measuring unit into the processing chamber, instead of the wafer105, and does not require special electrodes. Also, since this methodenables the quantity of light (namely, the potential difference) to beimmediately determined, actual processing can be executed using wafer105 before or after measurement, and spectral analyses on the status oflight emission from the plasma 106 can be easily conducted during,before, or after measurement. That is to say, the height of sample mount108, the potential difference inside the wafer, the plasma status at theparticular time, and wafer processing results can be obtained for oneset of parameters; and, as a result, the configuration of the equipmentcan be optimized in various terms (S1102 to S1108). Although the heightof the sample mount 108 is taken as an example in the description givenabove, this method is also valid for optimizing other factors, such asthe size of the sample mount, the position of the gas introducing port,and the size and position of the earth ring 114.

In addition, this method is valid for optimizing not only thehardware-like configuration of the equipment, but also the type ofprocessing gas, the pressure, the magnetic fields, the output power andfrequency of the microwave power supply, the output power and frequencyof the high-frequency power supply, and various other processingparameters (S1110 to S1116).

The etching apparatus shown in FIG. 1 is an example of the reactionchamber 901.

FIG. 12 is a schematic diagram of the potential difference and currentmeasuring unit 200 according to another embodiment of the presentinvention for a case in which a bias voltage is not applied. Themeasuring unit configuration in FIG. 12 differs from that of FIG. 2 inthat capacitor 202 for removing AC components is not provided. When nobias voltage is applied, AC components can be ignored, andconfigurations without capacitor 202 usually pose no problem. As amatter of fact, for a CVD or ashing unit, there are occasions when nobias voltage is applied, even during plasma processing.

An example of an ashing unit not requiring the application of a bias isshown in FIG. 13. Although the configuration shown in FIG. 13 is similarto that of FIG. 1, high-frequency power supply 109 and earth ring 114are absent in the configuration shown in FIG. 13. The type of gas usedto remove resist is an argon gas, an oxygen gas, or the like. When thepotential difference and current measuring unit shown in FIG. 12 isactually used, this measuring unit is introduced into a unit, such asthe ashing unit mentioned above.

In the potential difference and current measuring unit 200 of thepresent invention, one of the two antennas can also be routed through acircuit substrate. A modified version of the potential difference andcurrent measuring unit shown in FIG. 2 or FIG. 12 is shown in FIG. 14.In this case, one terminal of light-emitting diode (1401) ischaracterized in that it is routed through substrate 204. In generalsemiconductor manufacturing processes, the potential of the gate withrespect to that of the substrate is usually picked up as a problem. Inthe configuration described above, however, the voltages of thesubstrate and gate can be measured. Also, in this unit configuration,antenna 203, which is not routed through the substrate, is installed inthree places which are at different distances from the center of thewafer. Thus, the potential difference between antenna 203 and siliconsubstrate 204 can be detected.

In addition, a comb-shaped antenna can also be used instead. Thepotential difference and current measuring member shown in FIGS. 15A and15B is composed of two LEDs 201 connected in parallel in oppositedirections between comb-shaped antenna 1501 and antenna 203, and acapacitor 202 is connected in parallel to the LEDs. The measuring membershown in FIGS. 15A and 15B is located on and connected to insulatingfilm 205, with which the surface of silicon substrate 204 is covered. Inthis case, comb-shaped antenna 1501 is formed using resist 1502processed in line-and-space form on conductor antenna 203 positioned oninsulating film 205. The pattern of the line-and-space form on resist1502 is formed by lithography during semiconductor manufacturingprocesses, and the sizes of the lines and spaces are very small (severalmicrons or less). Modification of antenna 203 into structure such asthat of comb-shaped antenna 1501 enables measurement of the DC potentialdifference in the microstructure due to a phenomenon generally called“electron shading”. Since the flow of ions into the silicon substrate204 under a plasma state is accelerated, these ions enter the siliconsubstrate 204 almost vertically. In the meantime, electrons, because oftheir small mass, are great in random-oriented velocity due to heat,and, therefore, they flow from random directions to the siliconsubstrate 204.

For this reason, when resist 1502 with a microstructured patternconsisting of very small grooves and holes less than several microns insize is present on silicon substrate 204, although a large majority ofions arrive at the bottom of the microstructured pattern, a largemajority of electrons cannot reach the bottom. As a result, the bottomof its microstructured pattern is charged positively and the walls ofits microstructured pattern are charged negatively, and this phenomenonis called “electron shading”. During semiconductor device processing,the bottom of the microstructured pattern is usually connected to thegate oxide film, with the result that, since the gate is charged tocause insulation breakdown, the magnitude of the electron shading needsto be measured.

The comb-shaped antenna 1501 shown in FIGS. 15A and 15B has its siliconsubstrate 204 charged positively by electron shading, and, thereby, a DCpotential difference occurs between comb-shaped antenna 1501 and theantenna 203. One of two LEDs 201, therefore, emits light and theelectron shading level can be measured from the intensity of the light.During the measurement of the electron shading level, it is preferablethat the comb-shaped antenna 1501 and antenna 203 connected between twoLEDs 201 should be arranged close to one another so as to avoid theoverlapping of DC potential differences between positions. Also,measurements under the status that electron shading and the DC potentialdifference on the surface of silicon substrate 204 overlap can beperformed by spacing the comb-shaped antenna 1501 and the antenna 203.

The value of the current flowing into LEDs 201 can be obtained byarranging the comb-shaped antenna 1501 and planar antenna 203 close toone another and examining the intensity of the light emitted from LEDs201. The value of the current flowing into LEDs 201 is a quantitydetermined by the structure of the comb-shaped antenna 1501 and the ioncurrent density of plasma 106. Since the structure of the comb-shapedantenna 1501 is known, is the ion current density can be calculated byexamining the amount of light emitted within this measuring unit.

If antenna 203, after being made thicker than antenna 1501, is exposedto plasma and both antennas 203 and 1501 are etched, the light emittedfrom LEDs 201 can be observed while the antenna 1501 remains. Once theantenna 1501 has been etched, however, the current concentration areawill decrease and LEDs 201 will stop emitting light. The etching ratecan therefore be measured from the light emission duration of the LEDs201 and the thickness of the antenna 1501. Modification of the patternon resist 1502 enables the measurement of an etching rate dependent onthe new pattern, for example, a resist pattern with a new groove widthor with a plurality of holes.

Next, a method of improving the uniformity of the internal etching ratesfor the wafer surface by use of this measuring unit will be described.During the development of an etching apparatus or the determination ofetching parameters, the uniformity of etching rates is required tosatisfy predetermined standards for the entire wafer surface. Althoughconventional methods usually involve the use of interference to measureetching rates immediately, it is very difficult to observe the rates ina plurality of sections immediately at the same time for reasons such asthe limited installation position for a spectroscope. Also, when complexpatterns exist, simultaneous observation of etching rates is not easy,since it requires sophisticated calculation of diffraction with highaccuracy. Unlike such conventional methods, the method described belowis a very simple technique, since it only requires that theabove-mentioned measuring unit be installed in multiple places on thewafer and that the light emitted from light-emitting circuit 801 beobserved during etching.

The requirement that the uniformity of flat areas in etching rate overthe entire wafer surface should be high refers to the requirement thatfluctuations in the light emission duration of light-emitting circuit801 should be insignificant. Accordingly, in the plasma etchingapparatus of FIG. 1, when fluctuations in the light emission duration oflight-emitting circuit 801 are measured with each etching process underdifferent settings of parameters, such as the flow rate of the gas to beintroduced during etching, if the measured fluctuations areinsignificant, this means that the etching rates for the flat areas areuniform over the entire wafer surface.

An antenna with patterns can be easily constructed by resting amicropatterned insulating material on the conductor portion of theantenna. This insulating material may be, for example, the J5022-11capillary plate manufactured by Hamamatsu Photonix Corp. This capillaryplate has a plurality of holes 10 microns across and 400 microns deep.For actual semiconductors, problems usually occur when areas about onemicron or less in size undergo processing. However, according toReference [1] below, it is known that when the sizes, of the patternsare sufficiently smaller than typical sizes such as an average freestroke and a sheathing thickness, provided that the patterns areanalogous, equality in absolute size is not mandatory. That is to say,the use of the above-mentioned capillary plate or its processed orsimilar product enables the situation of the order of one micron to beeasily simulated without using lithography or the like.

Reference [1]: N, Mise et al., “Proceedings of the 5th InternationalSymposium on Plasma Process-Induced Damage”, p. 46, 2000.

Next, energy control based on the present invention will be describedwith reference to FIGS. 16A and 16B. A unit that has meshwork 1602 witha battery 1601 connected to the front of the antenna 203 and whichmeasures the energy of the charged particles entering the antenna, isshown as an embodiment in FIGS. 16A and 16B. A top view of the LEDmounted on the unit is shown as FIG. 16A, and a longitudinal section ofthe LED is shown as FIG. 16B. The battery is connected via hole 1603 ofinsulating film 205 to silicon substrate 204. The other terminal of theelement 801 is also connected to the substrate 204 through hole 1604.When a voltage is applied to meshwork 1602, a repulsive force is givento ions and electrons according to the particular direction andmagnitude of the application; and, as a result, only ions whose energyis greater than the applied voltage arrive at antenna 203. Thus, thenumber of charged particles having a predetermined energy level can bemeasured from the intensity of the emitted light and the voltage ofbattery 1601. In the arrangement of FIG. 16A, the distribution of energycan also be measured by installing multiple antennas equipped withbatteries 1602 of different voltages.

Next, another embodiment of the present invention will be described withreference to FIG. 17. This figure shows an example of measurement underdifferent surface area settings of antenna 203. In accordance with thismeasuring method, a sufficient current for activating the LED isrequired for the measurement of its light emission intensity. The upperlimit of the current is a value determined by the antenna area and thedensity of the plasma. Even when a sufficient current is supplied, ifthe potential difference across the LED is too low, its light emissionintensity is reduced by being limited according to the applied voltage.Whether the light emission intensity of the LED is limited by thevoltage or by the current is not univocally determined since the abovedepends on the current-voltage characteristics of the LED, the magnitudeof the potential difference on the wafer, the size of the antenna, thedensity of the plasma, and other factors. Although the surface area ofthe antenna needs to be adjusted to find the region where the lightemission intensity can be measured, a wide range of currents can bemeasured at the same time by providing beforehand, as shown in FIG. 17,a plurality of LEDs 201 connected to antennas 203 of different surfaceareas.

FIG. 18A is a diagram of an on-wafer potential difference measuring unit200, which represents another embodiment of the present invention. FIGS.18A and 18B are an enlarged top view and enlarged longitudinal sectionof this measuring unit. In this embodiment, measuring unit 200 uses thinoxide films as its light-emitting elements. On silicon substrate 204there is deposited an insulating layer 205, and thin gate oxide films1801 are provided as part thereof. Antenna 1802, made of poly-silicon orthe like, is connected to gate oxide films 1801. The thin oxide filmsemit light with a sufficient supply of current and can therefore be usedsimilarly to LEDs 201. Since this unit configuration is close to theconfiguration of a more practical semiconductor wafer processingapparatus, more accurate data measurements can also be obtained.

In the configuration of FIG. 18A, a plurality of light-emitting elementsdifferent in antenna surface area are arranged on a wafer. Although onlyone set of light-emitting elements are shown in the figure, it ispossible to arrange multiple sets over the entire wafer surface andmeasure the distribution of energy. Although it is intended to measurethe potential difference between antenna 1802 and silicon substrate 204,this configuration can also be varied to measure the potentialdifferences between any other two positions.

In addition, since the LEDs are made of silicon, not a compoundsemiconductor, they do not pose problems associated with pollution.Furthermore, during the manufacture of semiconductor devices using asilicon substrate, light-emitting circuit 801 can be formed in, forexample, a scribe area or an area not to be used as the semiconductordevice at the edge of a wafer, by forming LEDs by use of silicon. Theformation of a light-emitting circuit 801 in such areas is, in turn,effective for avoiding a decrease in the number of semiconductor deviceswhich can be obtained from one wafer. Furthermore, the use of this wafermakes it possible to measure the potential difference on the wafersurface under a plasma-exposed status and the degree of damage of thegate oxide film while creating devices. In short, it is possible toevaluate the status of the plasma apparatus and the processingparameters immediately and to estimate a device manufacturing yield.

Next, an embodiment of light-emitting circuit 801 is shown in FIG. 19.In this embodiment, two circuits are connected in parallel betweenantennas 203A and 203B. The first circuit consists of directly connectedlight-emitting element 1901 and Zener diode Z1 s, another Zener diode Z1p connected in parallel to the 1901—Z1 s connection, and diode D1connected to diode Z1 p. The diodes Z1 s and the Z1 p are polarized in aforward direction, and the diode D1 is polarized in the reversedirection to that of the diode Z1 s. The voltage at which a currentabruptly begins to flow when a reverse voltage is applied to the Zenerdiodes is taken as VZ. In this case, Zener diodes Z1 s and Z1 p areselected so that the absolute threshold voltage VZ1p of the Zener diodeZ1 p is greater than the absolute threshold voltage VZ1s of the Zenerdiode Z1 s. The second circuit, which consists of the same elements asthose of the first circuit, has all its polarized components reversedwith respect to the polarized components of the first circuit. In thiscase as well, Zener diodes Z2 s and Z2 p are selected so that theabsolute threshold voltage value VZ2p of the Zener diode Z2 p is greaterthan the absolute threshold voltage value VZ2s of the Zener diode Z2 s.Light-emitting element L1 is an element not having polarity, and L1 is,for example, an element that emits light when activated by the currentflowing into a filament made of tungsten.

The conditions where light-emitting element L1 emits light under thelight-emitting circuit composition shown in FIG. 19 are described below.Since L1 and D1 are connected in series, it can be seen that at least ifΔTV=VA−VB>0 holds, L1 will emit light. However, if the potentialdifference ΔV between A and B is smaller than the threshold value ofdiode D1, namely, if ΔV<VD1, no current flows into L1 because of theeffects of diode D1, and this also applies in the case of ΔV<VD1+VZ1s,even when the potential difference increases. The reason why no currentflows into L1 is that Zener diode Z1 s does not yield. When thepotential difference further increases (ΔV>VD1+VZ1s), Zener diode Z1 syields and a current begins to flow into L1. When the potentialdifference ΔV increases more significantly (namely, ΔV>VD1+VZ1p), Zenerdiode Z1 p also yields. Therefore, even when the potential difference ΔVincreases in the range of ΔV>VD1+VZ1p, the voltage between L1 and Z1 sis maintained at a constant value of VD1+VZ1p. This means that Zenerdiode Z1 p protects the circuit by preventing an overvoltage from beingapplied across light-emitting element L1 or an overcurrent from flowinginto L1. Accordingly, ΔV and the light emission intensity of L1 directlyvary when VD1+VZ1p<ΔV<VD1+VZ2p. When ΔV<VD1+VZ2p, however, the lightemission intensity is kept constant, irrespective of ΔV.

When a reverse voltage is applied, only light-emitting element L2 emitslight and L1 and L2 do not emit light simultaneously.

Consider a case in which, more specifically, the HZ6A1 Zener diodes,manufactured by Hitachi, Ltd., are used as Zener diodes Z1 s and Z2 s,the HZ7A1 Zener diodes, manufactured by Hitachi, Ltd., are used as Zenerdiodes Z1 p and Z2 p, and the HSK110 diodes, manufactured by Hitachi,Ltd., are used as diodes D1 and D2. According to the Hitachi Databookissued in September 1992, the yield voltages of the HZ6A1 and HZ7A1diodes are 5.2 V and −6.3 V, respectively, and the threshold voltagevalue of the HSK110 is 0.8 V. At this time, when the potential VA of theantenna A becomes 6.0 V higher than the potential VB of the antenna B,the light-emitting element L1 emits light. When the difference betweenVA and VB is smaller than 7.1 V, the light emission intensity of L1changes according to the voltage applied thereto. When the differencebetween VA and VB becomes equal to or greater than 7.1 V, the voltageapplied to L1 no longer changes and the light emission intensity becomesindependent of the potential difference. When VA and VB are opposite inpolarity, L2 emits light.

Diodes can also be used as alternatives for the Zener diodes. Ingeneral, the threshold voltage values of the diodes are about 1 V, andthey do not change too significantly. For this reason, a plurality ofdiodes need to be connected in series to obtain threshold values fallingwithin the desired range.

A modified version of the embodiment of FIG. 19 is shown in FIG. 20. Inthis version, four circuits are connected in parallel between antennas203A and 203B. The first circuit consists of light-emitting element L1,Zener diode Z1, and diode D1, which are all connected in series. TheZener diode Z1 and the diode D1 are opposite in polarity. The secondcircuit, which includes light-emitting element L2, has the samecomposition as that of the first circuit, and all of its polarizedcomponents are reversed with respect to the polarized components of thefirst circuit. The third circuit consists of Zener diodes Z1 p and Z2 pconnected in series, which are reversed in polarity with respect to oneanother. The fourth circuit consists only of capacitor C.

The light-emission condition of element L1 in such circuit compositioncan be expressed as VA−VB>VZ1s+VD1. The voltage applied to element L1 atthis time can be expressed as (VZ1p+VZD2 p)+(VZ1s+VD1), and the presentinvention, as with the embodiment of FIG. 19, provides a light-emittingelement circuit protection function.

In FIGS. 19 and 20, when Zener diode Z1 p (Z2 p) connected in parallelto light-emitting element L1 (L2) is omitted, since the voltage appliedto light-emitting element L1 (L2) is not limited, the light emissionintensity and the VA−VB difference directly vary in the light emissionrange. Therefore, the potential difference between antennas A and B inthe entire light emission range can be detected by measuring the lightemission intensity. In this case, however, the possible flow of anovercurrent into light-emitting element L1 (L2) may damage the elementL1 (L2).

In FIGS. 19 and 20, when diode D2 is omitted, the light-emitting elementL2 emits light if VA−VB>VZD2. That is to say, both L1 and L2 emit lightif VA−VB>VZD2 and VA−VB>VZ1+VD1. At this time, the VA−VB range can befurther limited according to the light-emission conditions of L1 and L2.

In FIGS. 19 and 20, when Z1 s (Z2 s) is omitted, the light-emittingelements L1 and L2 emit light if VA−VB>VD1 and VB−VA>VD2, respectively.

Next, the protection circuit 3 will be described with reference to FIG.21. When the fact of VA>VB is known, light-emitting circuit compositioncan be simplified. For example, a case in which Zener diode Z2 p isomitted from the embodiment of FIG. 20 is shown in FIG. 21. At thistime, when elements are selected so that 0<VZ1+VD1<VZ2+VD2<VZ3 holds,only the light-emitting element L1 emits light under the condition ofVA−VB>VZ1+VD1, and both L1 and L2 emit light under the condition ofVZ1+VD1<VA−VB<VZ2+VD2. Also, since the maximum voltage applied to thelight-emitting element L1 (L2) is VZ3+VZ1+VD1 (VZ3+VZ2+VD2), L1 (L2) isprotected. It is possible to measure VA−VB by observing the intensity ofthe light emitted from L1 and L2.

The appropriate light-emitting circuit can be formed by adjusting thenumber of elements or combining them in the light-emitting circuits ofFIGS. 19, 20, and 21, as required. In FIGS. 19, 20, and 21, although thelight-emission voltage is described with reference to miniature lamps(or the like as the light-emitting elements), LEDs and other elementsthat have diode characteristics that slightly change in thresholdvoltage may be used. The principles of operation, however, are asdescribed above. Also, when diodes are used as the light-emittingelements, diode D1 or D2 in series with respect to the elements in theembodiment of FIGS. 19, 20, and 21 is to be polarized in the samedirection.

FIG. 22 shows a unit having a directly connected resistor 2201 to adjustthe voltage applied to LED 801. This circuit composition can be usedwhen the potential difference on the wafer is too great. Current I canbe derived from the light emission intensity of LED 801. Voltage V1across the LED can be derived from the current-voltage characteristicsof the LED, and the voltage V2 across the resistor can be derived fromI×R. The developed potential can be derived from V1+V2. In this circuitcomposition, a wide range of voltages can be measured at the same timeby connecting resistors 2201 (R1 and R2) having different values to therespective LEDs 801.

FIG. 22 is a circuit diagram showing the fifth embodiment of thepotential difference and current measuring portion used for potentialdifference measurement based on the present invention. This figure showsanother example of a circuit composition intended to extend the range ofthe DC potential differences which can be measured using the potentialdifference and current measuring portion, and the resistance elementsfor limiting the flow of current into LEDs 801 are connected in series.

As shown in FIG. 22, the potential difference and current measuring unit200 has resistance elements connected in series to a parallel-connectedcircuit consisting of LEDs 801. Since resistance elements 2201 areconnected, this prevents an overcurrent from flowing into LEDs 801, andthe DC potential difference between conductor antennas 203A and 203B isvoltage-divided into the terminal-to-terminal voltage of LEDs 801 andthe terminal-to-terminal voltage of resistance elements 2201. Thus, thevoltage applied to LEDs 801 can be reduced below the DC potentialdifference between conductor antennas 203A and 203B, and the range ofthe DC potential differences which can be measured using the potentialdifference and current measuring unit can be correspondingly extended.

And, in this case as well, since the light emitted from LEDs 801 can bedetected visually or through a CCD camera or the like, separateconnection lead wires or probes are not required for the acquisition ofthe detection output signals.

Next, an observing method different from the above-described method ofobserving the light-emitting element through window 103 will bedescribed. In the etching apparatus shown in FIG. 23, a measurement hole2301 for a radiation temperature gauge is usually provided on samplemount 108 in order to measure the temperature of the silicon substrate204. If no such hole is provided, sample mount 108 needs to be providedwith a hole 2301 for observing the substrate 204. The intensity of lighton substrate 204 can be observed using hole 2301, which extends to thesurface of sample mount 108. At this time, when the appropriatelight-emitting circuit 801 is selected so that the light emitted fromlight-emitting circuit 801 passes through the substrate 204, thissubstrate can be observed from the reverse side without ever having toprovide the substrate with a hole. Similarly to the case in which thelight emission status of light-emitting circuit 801 is observed from thesurface of substrate 204, a camera 2302, an interference filter, apersonal computer, and/or optical fibers are to be used as required.

Silicon, for example, has the property that it transmits light whosewavelength is about 1.3 microns or more. When substrate 204 is composedprincipally of silicon, therefore, the use of the L1450-35C LED having awavelength of 1,450 nm makes it possible for the emitted light on thesurface of substrate 204 to be observed from the reverse side of thissubstrate without ever having to provide it with a hole. This circuitcomposition, in such case, makes it unnecessary to provide theobservation window 112.

The potential difference and current measuring unit of the presentinvention can be installed in various places. More specifically, thepackaging of the potential difference and current measuring unit whenmounted on an insulating object enables this package to be installed atany position and in any number of places. This package can also beinstalled on the inner wall of semiconductor manufacturing equipment toobserve the status of this inner wall. The package usually also can beinstalled in an area not directly exposed to the effects of the plasma.This area includes, for example, the side of the sample mount 108, thewall surface of the reaction chamber facing the sample mount, or aposition (say, 2401) directly above the vacuum-exhaust pump for thereaction chamber. The reason for this is to interrupt wafer processingimmediately on detection of an unusual state during plasma monitoringand then provide corrective measures in order to return the plasma to anormal state. These measures refer to, for example, exposing thereaction chamber to the atmosphere and cleaning the wall of the reactionchamber and the flow channel of the exhaust system using an organicsolvent or the like. Also, the potential difference between any twopoints can be measured using a package installed on the inner wall (forexample, at position 2402) of waveguide 102.

Basically, the antennas are formed using conductors. For minimum metalpollution, however, impurity-doped polycrystal silicon or a light metal(such as aluminum) or a highly electroconductive carbon should be usedas the antenna material.

LEDs are usually made of a compound semiconductor such as galliumnitride (GaN) or AlGaN, but if such LEDs are inserted in externallyexposed form into silicon-based semiconductor manufacturing equipment,metal pollution will result. To avoid this problem, the necessarysection should be shielded with a suitable material which enablesemitted light to be observed. Examples of this material include siliconoxide, plastic resin, and so on.

Next, an example of a GaAs light-emitting element is shown in FIGS. 25A,25B, and 25C, which are diagrams showing the potential difference andcurrent measuring unit 200 used for potential difference measurementbased on the present invention, and showing an example of a potentialdifference and current measuring unit integrated with substrate 204thereon. A top view of such a measuring unit is shown as FIG. 25A; across-sectional view taken along line A-A′ of FIG. 25A is shown in FIG.25B; and a cross-sectional view taken along line B-B′ of FIG. 25A isshown in FIG. 25C.

The potential difference and current measuring unit 200 shown in FIGS.25A to 25C has a potential difference and current measuring portionformed on the substrate 204 consisting of gallium arsenic (GaAs) andother substances. Light-emitting diodes consisting of n-typesemiconductor area 2501 and p-type semiconductor area 2502 are formed onthe substrate 204 by use of a method, such as ion implantation, and thisp-n junction emits light. The first insulating film 2503 is formed onthe substrate including the LED forming portion, and holes 2504 and 2505that lead to substrate 204 are provided in the n-type semiconductor area2501 and p-type semiconductor area 2502 of the first insulating film2503. One end of the first conductor 2506 is connected to p-typesemiconductor area 2502 through hole 2505, and the other end is routedalong the first insulating film 2503.

One end of antenna 203A is connected to n-type semiconductor area 2501through hole 2504, and the other end is routed along the firstinsulating film 2503. The conductor antenna 203B, after being connectedto the other end of the first conductor 2506, is formed on the firstinsulating film 2503. The second insulating film 2507 is formed on partof the other conductor antenna 203B. The second conductor 2508, afterbeing connected to conductor antenna 203A, is formed on the secondinsulating film 2507. The third insulating film 2509 is formed so as toensure that the exposed portions of the first conductor 2506, the secondconductor 2508, and conductor antenna 203B are covered with theinsulating film, and that the first conductor 2506 and conductor antenna203A are electrically insulated. In this case, the portion whereconductor antenna 203B and the second conductor 2508 are arranged so asto face one another via the second insulating film 2507 constitutes acapacitor, which is connected in parallel to an LED.

According to this embodiment, since the LED emits light according to theparticular DC potential difference between conductor antennas 203A and203B on substrate 204, the DC potential difference can be measured bydetecting the intensity of the emitted light.

In this case, the use of a light-transmitting substance (such as apoly-silicon) to form the second conductor 2508 and the third insulatingfilm 2509 enables light to be radiated to the outside. Light canlikewise be radiated to the outside by providing in its path a windowthat is covered with a transparent insulating film.

A light-emitting diode (LED) can likewise be formed by forming conductorantennas 203A and 203B on silicon substrate 204, or by forming acapacitor first, then embedding an LED microchip in the conductorantennas 203A/203B forming area or capacitor forming area by ion beamprocessing. Thus, a circuit of the same composition as that describedabove can be formed.

Although the embodiments described heretofore represent examples ofmeasurement in a plasma etching apparatus, the present invention alsoenables similar measurement with a film deposition apparatus, a resistremoval apparatus, and the like.

In addition, although the embodiments of semiconductor manufacturingequipment that have been described heretofore relate to a plasma sourcethat mainly uses magnetic fields and microwaves, the invention canlikewise be applied to other types of equipment that use a plasmasource, such as equipment that uses high-frequency inductive coupling orcapacitive coupling to generate a plasma, or equipment that useselectromagnetic waves of the UHF band to generate a plasma.

As described above, according to the present invention, it is possibleto provide a potential difference and current measuring method thatenables the DC potential difference on a target object to be measuredusing a simple means and a potential difference and current measuringportion of a simple configuration. In other words, it is possible tosupply a means by which important quantities in a semiconductor surfacetreatment apparatus, that uses plasma, namely, the plasma potentialdifference and plasma current occurring on the surface of a wafer, aremeasured without the modification of the apparatus. Since the use of acamera enables non-contact measurement of emitted light intensity, thelead-in terminals for lead wires that are always required inconventional probing methods become unnecessary. In addition, since thetarget wafer does not require lead wire connection, wafers can bechanged in the same way as performed for etching.

Furthermore, according to the present invention, it is possible tosupply a highly efficient sample processing method that uses a potentialdifference and current measuring portion of a simple configuration.

1. A method of measuring a potential difference for plasma processingwith a plasma processing apparatus that processes a sample byintroducing a gas into a vacuum chamber and generating plasma, whereinthe method comprises the steps of: positioning a measurement-use samplein the vacuum chamber, wherein a light-emitting element having a pair ofantennas is formed on the measurement-use sample; measuring an intensityof light emitted from the light-emitting element according to aparticular level of the current which flows into said light-emittingelement according to a potential difference that has been generatedacross the light-emitting element; and measuring the potentialdifference on the measurement-use sample according to a particular lightintensity.
 2. A method of measuring plasma currents for plasmaprocessing during which plasma processing of a sample is accomplished byintroducing a gas into a vacuum chamber and generating plasma, whereinthe method comprises the steps of: positioning a measurement-use samplein the vacuum chamber, wherein a light-emitting element having a pair ofantennas is formed on the measurement-use sample; measuring a flow ofcharged particles from the plasma to a surface of said measurement-usesample as an intensity of light emitted from the light-emitting elementaccording to a particular level of current flowing into thelight-emitting element; and measuring an amount of current flowing intothe light-emitting element according to a particular light intensity. 3.A sample processing method intended to process a sample by introducing agas into vacuum chambers and generating plasma, wherein the sampleprocessing method comprises the steps of: positioning a measurement-usesample in the vacuum chamber, wherein a light-emitting element having apair of antennas is formed on the measurement-use sample; measuring anintensity of the light emitted from the light-emitting element accordingto a particular level of current; measuring a potential difference onthe measurement-use sample according to the measured light intensity;measuring the potential difference using the measurement-use sample eachtime the sample within the vacuum chamber is processed a required numberof times; and interrupting the processing of samples if the measuredpotential difference exceeds a particular value.
 4. A sample processingmethod intended to process a sample by introducing a gas into a vacuumchamber and generating plasma, wherein said sample processing methodcomprises the steps of: positioning a measurement-use sample in thevacuum chamber, wherein a light-emitting element having a pair ofantennas is formed on the measurement-use sample; measuring a flow ofcharged particles from the plasma to a surface of the measurement-usesample as an intensity of light emitted from the light-emitting elementaccording to a particular level of current flowing into thelight-emitting element; measuring an amount of the current flowing intothe light-emitting element according to the particular light intensity;measuring a plasma current using the measurement-use sample each timethe sample within the vacuum chamber is processed a required number oftimes; and interrupting the processing of the samples if the measuredplasma current exceeds a particular value.
 5. An apparatus for measuringplasma potential differences and currents in a plasma processingapparatus that provides a sample with plasma processing by introducing agas into vacuum chambers and generating plasma, wherein said potentialdifferences and currents measuring apparatus comprises: a light-emittingelement, having a pair of antennas, formed on a measurement-use sample,wherein a current is allowed to flow into said light-emitting elementaccording to a potential difference that has been generated across thelight-emitting element, a light intensity measurer for measuring anintensity of light emitted from the light-emitting element according toa particular level of the current; and a potential difference measurerfor measuring the potential difference on the measurement-use sampleaccording to the particular light intensity.
 6. An apparatus formeasuring plasma potential differences and currents in a plasmaprocessing apparatus that provides a sample with plasma processing byintroducing a gas into vacuum chambers and generating plasma, whereinthe potential differences and currents measuring apparatus comprises: alight-emitting element, having a pair of antennas, formed on ameasurement-use sample; a light intensity measurer for measuring a flowof charged particles from the plasma to a surface of the measurement-usesample as an intensity of light emitted from the light-emitting elementaccording to a level of current flowing into the light-emitting element;and a current measurer for measuring the amount of current flowing intothe light-emitting element according to a particular light intensity.